Method of and apparatus for reducing engine vibration



sept.. l,

Filed June 18. 1920 Patented Sept. 1 1925.

UNITED STATES PATENT OFFICE.

WILLARD c. xREss, or BUrrAL'o, NEW Yonx.

l.Application led .Tune 18, 1920. Serial No. 389,912.

To all 'whom z't may concern:

Be it known that I, WTLLARD C. KREss, a citizen of the United States,residing at Buffalo, in the county of Erie and State of New York, haveinvented new and useful Improvements in Methods of and Apparatus forReducing Engine Vibration, of which vvthe following is a specification.

This invention relates to multicylinder engines and more particularly tointernal combustion engines of the single acting type such as areemployed in automobiles.

The object of the invention is the provision vof a novel method of-andapparatus for reducing vibration of the engine and increasing itseiciency.

In its preferred embodiment, the improvements consist essentially inmaking the usual crank case air or fluid-tight and creating andmaintaining a `fluid pressure therein. to provide a sustaining mediumunder the pistons, and in order that ascending pistons of the engine maybe returned largely by descending pistons through the intervening bodyof compressed fluid, lthus lgreatly relieving the crank-shaft from thereciprocating load. and diminishing vibration.

The accompanying drawing represents ar posed between these sections torender thecrank case practically air tight.

Jcurnaled in. bearings 12 in the upper section of the crank case is the'engine crankshaft 13 and bolted to the upper side of said section is thecylinder block 14 in which the pistons 15 reciprocate, the'latter beingconnected to the crank shaft by the usual connecting rods 16, so thatsome of the pistons ascend while others descend.` Suitable packing 17 isinterposed betweenl the 'cylinder block and the upper crank case section10 to insure a pressure tight/jointA 'between' these parts.

In order to form a pressure tight joint at the rear end of the crankcase where the crank shaft 13 projects therethrough, packing rings 18are provided on said shaft which are ittcd the bore of a' col1ar19suitably 'secured to the rear wall of the crank case.

The several engine-cylinders open at their lower ends into the crankcase, in a manner common to this typeof engine.

lThe means for producing and maintaining a fluid pressure in thecrank-case, are preferably constructed las -followsz- Bolted orotherwise secured to the front end of the crank case so as to form apressure-tight joint therewith, isl an air .or pres-l sure pump 20, inthe base 21 of which is 6 5 journaled an auxiliary crank shaft 22preferably driven from the main crank shaft 13 of the engine. As'shownin the drawing, the front end of the engine crank shaft is provided witha reduced extension 23 which projects through .the front wall of thecrank case and to which the adjacent bored end 24of the auxiliary crankshaft 22 is connected by a key 25 or other suitable r means. Toestablish a` pressure-tight joint 7 4 at the front end of the crank casewhere the engine' crank shaft projects therethrough packing rings 26'aremounted on the rear end 24 of the auxiliary crank shaft 22 which arefitted in the bore of`a collar 27 suitably 80 `secured to the adjacentwall of the engine crank case.

28 represents the cylinder of the pressure pump in which the piston 29reciprocates the latter being connected to the crankshaft 22 by aconnecting rod 3Q. .Arranged in the cylinder head 31 is a port 32communiL eating with the atmosphere 4and controlled by an inlet valve 33which opens inwardly by the suction produced on the downward stroke ofthe piston of said cylinder. This valve is ,yieldingly held to its seatby a spring 34 surrounding the stem 35 of the valve and bearing at itslower end against the top of the cylinder head and at its upper endagainst a washer 36 adjustably held on the stem by a nut 37. 38indicates the outlet port of the pump controlled by a valve 39, whichopens outwardly by thepressure produced in the cylinder on the upwardstroke of the piston', and whichisyielding- Iy held to its seat by aspring 40 surrounding the stem 41 of said valve which is pref-` erablyguided in a plug 42 screwed into the 105 upper side of the cylinderhead. The air expelled through the Outlet port 38 enters a chamber 43 inthe Cylinder had which 48 of the valve and adiust-ably mounted thereonby a nut 49.

The operation of the engine is as follows:

Assuming the engine to be running, the pump-shaft 22 is compelled toturn with the engine crank shaft 13, reciprocating the pump-piston 29.On the downward stroke of this piston, air under atmospheric pres.- sureenters the pump cylinder through the` port 32, and on its upward strokesaid piston expelsthe air from the cylinder through the outlet port 38into the chamber 43 and thence through the passage 44 into the enginecrank-case. Thus, a pressure is built up in said case which acts as avpower-transmitting Huid or cushion between the adjacent ends of theseveral pistons, whereby a portion of the explosion-pressure exerted ona descending piston is simultaneously exerted through the cushion on anascending vpiston to effect its return stroke, with the result that thestrain .or reciprocating load incident to raising or returning thepistons is'largely removed from the crank shaft and the connecting rods,thus reducing vibration to the minimum. This cushioning or pressuremedium acts with equa-l pressure on the bottoms of theascending anddescending pistons, which are all of equal areas, and

the pressure is thus neutralized and does not retard the movement of thepistons. It is evident that such pressure maintains a constant upwardtorque or pull on the crank shaft, connecting rods and pistons, butwithout resisting rotation of said crank shaft or movement of thepistons. The explosive forceor pressure acting on a descending pistondoes not turn the crank shaft solely through the customary direct thrustof the piston and connecting rod, but a considerable portion of thatforce is exerted indirectly on the crankshaft through the moving. ordisplaced air cushion which acts ou the ascending piston or pistons andcauses them to pull upward on the cranks of the shaft. While theexplosion stroke is thus transmitted to the crank shaft partly1 throughthe ascending-piston or pistons, it

. is evident that the shaft is relieved'from a considerable part of thereciprocating load, beca-use, after descending, a piston is notreturned.' solely by the connecting rod and Crank pin but is in a greatmeasure r6' turned by the descending piston and the movmg air cushion.It follows that vibra-' necting rods, resulting in destructive wear andvibration. By providing a sustaining and transmitting medium ofcompressed air or similar fluid under and between the pistons,suchreciprocating load or the strain of the'return stroke of the piston istaken olithe crank shaft,.as above explained, reducing vibration andsecuring the above-mentioned advantages.

Any required pressure may be maintained. in the crank case by adjustingthe nut 49 to increase or decrease the tension of the spring 4:

The degree of' air pressure necessary t0 neutralize the inertia loads atthe vforward end'of the'piston stroke is dependent upon the effectivearea of the piston and the weight of the reciprocating mass, and tosecure maximum eiiiciency, it is ldesirable to vary the pressureaccording to the speeds, since it is apparent that greater pressure is lrequired at high speeds than at low speeds.,

The most eiicient pressure for any given speed can readily be determinedin practice, and is merely a matter of adjusting the regulating nut 49.For example, an engine having a cylinder with a three-inch bore and athree-inch stroke, with a reciprocating `mass weighing two pounds and acrank rotating at a speed of 4,00() R. P. M., will require a fluidpressure in the crank case of approximately one hundred and forty poundsto the square inch.

It will be observed that the fluid-tight crank case forms afluid-pressure chamber or conduit with which the adjacent open ends ofthe several engine cylinders communicate and byI which they areconnected, so that thel pressure fluid acts as a powertransmittingmedium between'the descending and ascending pistons whose lower ends areexposed thereto.

The engine cylinders as well as the crank case are fluid-tight at alltimes, and a practically constant and uniform air pressure or tension istherefore maintained in the crank case and against the lower ends of thepistons throughout their forward and backward strokes.

I claim as my invention:

1.k The herein described method of relieving the crank shaft of a singleacting multiple-cylinder Iinternal combustion en ine from thereciprocating load to reduce vi ration, which consists in transmittingthe Lasagni 8h posed medium of compressed Huid, confined front ends ofthe oppositely-moving pis- 10 under pressure. tons being exposed to thepressure-medium 2. The combination of a single acting in said conduit,whereby the movement of a multicylnder internal combustion engine,descending piston is transmitted to an as- 5 a fluid pressure conduitcommunicating with cending piston by said pressure-medium,

and'connecting the engine cylinders, said and means for producingfluidfpressure in u conduitl and said cylinder being fluid-tight to saidconduit. prevent the release of Huid and maintain a substantiallyconstant pressure therein, the WILLARD C. `KRESS.

